Structure and disorder in Pb‐Na metasilicate (PbO:Na₂O:2SiO₂) glasses: A view from high‐resolution ¹⁷O solid‐state NMR

Abstract

Knowledge of the structure of lead (Pb)-bearing silicate glasses, such as degree of polymerization and arrangement among cations, provides improved prospects for understanding their macroscopic properties. Despite the importance, the detailed disorder in Pb-bearing silicate glasses with varying composition (i.e., Pb/alkali content) has not been systematically explored. Here, we reveal the first unambiguous structural information of PbO-Na 2 O-SiO 2 glasses with varying PbO content [i.e., X PbO = PbO/(Na 2 O + PbO)], which are the fundamental model system for multicomponent Pb-bearing glasses, using high-resolution 17 O solid-state NMR. 17 O NMR spectra clearly show the resolved multiple oxygen sites, such as Na-O-Si, Si-O-Si, and [Na,Pb]-O-Si. As X PbO increases, the fraction of [Na,Pb]-O-Si peak increases markedly at the expanse of substantial reduction in the fraction of Na-O-Si/ total NBO. This trend indicates the relative predominance of the dissimilar pairs around non-bridging oxygen (NBO) and, therefore, can be explained well with the pronounced chemical ordering among Na + and Pb 2+. These results confirm that Pb is primarily a network-modifier in the glasses studied here. Atomic environments around both NBO and BO are affected by the change in Na/Pb ratio, while topological disorder due to cation mixing around NBO is much more prominent in Pb endmember. The structural details of short-range configurations around oxygen in alkali Pb-silicate glasses provide atomistic insights for understanding the properties of Pb-bearing multicomponent silicate glasses.